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/*
* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
* Copyright (C) 2007 The Regents of the University of California.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
* For details, see <http://zfsonlinux.org/>.
*
* The SPL is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* The SPL is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with the SPL. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _SPL_MUTEX_H
#define _SPL_MUTEX_H
#include <sys/types.h>
#include <linux/mutex.h>
#include <linux/compiler_compat.h>
#include <linux/lockdep.h>
typedef enum {
MUTEX_DEFAULT = 0,
MUTEX_SPIN = 1,
MUTEX_ADAPTIVE = 2,
MUTEX_NOLOCKDEP = 3
} kmutex_type_t;
typedef struct {
struct mutex m_mutex;
spinlock_t m_lock; /* used for serializing mutex_exit */
kthread_t *m_owner;
#ifdef CONFIG_LOCKDEP
kmutex_type_t m_type;
#endif /* CONFIG_LOCKDEP */
} kmutex_t;
#define MUTEX(mp) (&((mp)->m_mutex))
static inline void
spl_mutex_set_owner(kmutex_t *mp)
{
mp->m_owner = current;
}
static inline void
spl_mutex_clear_owner(kmutex_t *mp)
{
mp->m_owner = NULL;
}
#define mutex_owner(mp) (ACCESS_ONCE((mp)->m_owner))
#define mutex_owned(mp) (mutex_owner(mp) == current)
#define MUTEX_HELD(mp) mutex_owned(mp)
#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))
#ifdef CONFIG_LOCKDEP
static inline void
spl_mutex_set_type(kmutex_t *mp, kmutex_type_t type)
{
mp->m_type = type;
}
static inline void
spl_mutex_lockdep_off_maybe(kmutex_t *mp) \
{ \
if (mp && mp->m_type == MUTEX_NOLOCKDEP) \
lockdep_off(); \
}
static inline void
spl_mutex_lockdep_on_maybe(kmutex_t *mp) \
{ \
if (mp && mp->m_type == MUTEX_NOLOCKDEP) \
lockdep_on(); \
}
#else /* CONFIG_LOCKDEP */
#define spl_mutex_set_type(mp, type)
#define spl_mutex_lockdep_off_maybe(mp)
#define spl_mutex_lockdep_on_maybe(mp)
#endif /* CONFIG_LOCKDEP */
/*
* The following functions must be a #define and not static inline.
* This ensures that the native linux mutex functions (lock/unlock)
* will be correctly located in the users code which is important
* for the built in kernel lock analysis tools
*/
#undef mutex_init
#define mutex_init(mp, name, type, ibc) \
{ \
static struct lock_class_key __key; \
ASSERT(type == MUTEX_DEFAULT || type == MUTEX_NOLOCKDEP); \
\
__mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
spin_lock_init(&(mp)->m_lock); \
spl_mutex_clear_owner(mp); \
spl_mutex_set_type(mp, type); \
}
#undef mutex_destroy
#define mutex_destroy(mp) \
{ \
VERIFY3P(mutex_owner(mp), ==, NULL); \
}
#define mutex_tryenter(mp) \
({ \
int _rc_; \
\
spl_mutex_lockdep_off_maybe(mp); \
if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) \
spl_mutex_set_owner(mp); \
spl_mutex_lockdep_on_maybe(mp); \
\
_rc_; \
})
#ifdef CONFIG_DEBUG_LOCK_ALLOC
#define mutex_enter_nested(mp, subclass) \
{ \
ASSERT3P(mutex_owner(mp), !=, current); \
spl_mutex_lockdep_off_maybe(mp); \
mutex_lock_nested(MUTEX(mp), (subclass)); \
spl_mutex_lockdep_on_maybe(mp); \
spl_mutex_set_owner(mp); \
}
#else /* CONFIG_DEBUG_LOCK_ALLOC */
#define mutex_enter_nested(mp, subclass) \
{ \
ASSERT3P(mutex_owner(mp), !=, current); \
spl_mutex_lockdep_off_maybe(mp); \
mutex_lock(MUTEX(mp)); \
spl_mutex_lockdep_on_maybe(mp); \
spl_mutex_set_owner(mp); \
}
#endif /* CONFIG_DEBUG_LOCK_ALLOC */
#define mutex_enter(mp) mutex_enter_nested((mp), 0)
/*
* The reason for the spinlock:
*
* The Linux mutex is designed with a fast-path/slow-path design such that it
* does not guarantee serialization upon itself, allowing a race where latter
* acquirers finish mutex_unlock before former ones.
*
* The race renders it unsafe to be used for serializing the freeing of an
* object in which the mutex is embedded, where the latter acquirer could go
* on to free the object while the former one is still doing mutex_unlock and
* causing memory corruption.
*
* However, there are many places in ZFS where the mutex is used for
* serializing object freeing, and the code is shared among other OSes without
* this issue. Thus, we need the spinlock to force the serialization on
* mutex_exit().
*
* See http://lwn.net/Articles/575477/ for the information about the race.
*/
#define mutex_exit(mp) \
{ \
spl_mutex_clear_owner(mp); \
spin_lock(&(mp)->m_lock); \
spl_mutex_lockdep_off_maybe(mp); \
mutex_unlock(MUTEX(mp)); \
spl_mutex_lockdep_on_maybe(mp); \
spin_unlock(&(mp)->m_lock); \
/* NOTE: do not dereference mp after this point */ \
}
int spl_mutex_init(void);
void spl_mutex_fini(void);
#endif /* _SPL_MUTEX_H */
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